Recent reports indicate that vagal nerve innervation of hepatic parenchymal cells exists and that such innervation may exert a control on certain enzymatic activities. We aim to prove that vagal nerve innervation is essential to initiate and/or maintain the orderly process of hepatic regeneration following partial hepatectomy. This will be shown primarily by following the sequence of Thymidine incorporation into DNA during regeneration in intact and vagotomized rats. Differential effects upon RNA (and protein) will also be determined primarily using orotic acid followed by the phenol extraction and subsequent purification and characterization of nuclear and cytoplasmic RNA.